1. Field of Invention
This invention relates to kinetic liquid pumps as an improvement means in order to obtain greater performance, including higher head pressures at high flow rates, as well as allowing performance and efficiency in varying flow and pressure requirements with a single pump.
Traditionally, centrifugal pumps have dominated the kinetic liquid pumping field; however, the geometry of centrifugal pumps presents some problem areas, which I have endeavored to correct with this invention. The areas I am referring to are typical to centrifugal pump geometry.
2. Description of Prior Art
A typical centrifugal pump has an axial intake and a volute surrounding the rotor as a discharge. The intake always communicates with the discharge. Pumping is provided by force from vanes, which spiral outward in increasing angle with a radius from the axis of rotation. Diverging fluid channels are formed between adjacent vanes with a narrow opening at the intake side and a wide opening at the axially outer extremity. This geometry causes some problems in pumping fluids. A first problem exists at the entrance to the fluid channels due to the proximity of adjacent vanes constituting a flow restriction. By Bernoulli's Law, as the fluid is restricted, the velocity is increased, and the pressure drops. Since the pressure at this point is the lowest in the system, any further pressure drop may go below the fluid vapor pressure, causing the liquid to vaporize and cause cavitation in the pump, an undesirable state, which can cause pump damage and failure. This problem is referred to by the industry as “suction specific speed,” meaning that the rotational speed of the pump is restricted by this problem. A second problem in geometry is that the vanes at this point are at an angle, which is beginning more radial and as the rotor diameter is increased becomes more tangential. This is probably because the vanes are expected to act in a similar manner to a propeller with changing pitch to continuously accelerate the fluid, in this case radially outward into the discharge volute. Having the vanes act as a radial propeller creates some problems such as contributing to the formation of vacuum on the side of the vane not acting on the fluid and further being a cause of cavitation, and on the leading face of the vane, the force of the vane on the fluid causes shear and causes the fluid to assume a rolling motion as it traverses the divergent fluid passage between vanes. This causes a rolling vortex of increasing diameter as the fluid approaches the end of the fluid passage and enters the volute. The main problem to this is that as the vortex enters the volute, the direction of motion of the outer velocity vector of the vortex is in the opposite direction to the flow in the volute toward discharge. This was verified by a computer simulation, which showed a total reversal of direction due to this effect, when micro particles simulate the liquid. This particular failure is called “re-circulation” within the industry. Another paradox is the divergent nature of the fluid passage between vanes. Because the passage is divergent, the fluid is slowing down, again due to Bernoulli's Law. But the rotor vanes are trying to speed it up. This accounts for most of the development of vortices in the passages apparently.
The apparent objective of the centrifugal geometry is to force the fluid axially outward into the volute by action of the vane fan blades. One has to then ask if this is a good objective. Pushing the fluid outward in a 360 degree manner into a volute, which then converts the radial direction of flow to a single direction, seems illogical, at least to this inventor, as it doesn't directly move the fluid flowing in the same direction, which is out the discharge duct. This geometry is similar to a light bulb, which requires various reflectors to try to collimate the light beam rather than have it already focused. It is like the difference between a light bulb and a laser.
Finally, the centrifugal pump does not appear to take advantage of the other engine, which works to drive the pump, the atmospheric pressure engine. It attempts to overcome the atmospheric engine by force, rather than by taking advantage of naturally occurring forces. I have attempted to rectify these problems seen with the prior art in as simple and as logical ways as possible, primarily by changing the vane geometry, and by making the pump positive displacement by eliminating the volute which allows the pressure to build within the fluid chamber, becoming stratified in an axial pressure gradient. And forming cylindrical isobars, which can replace solid surfaces. These isobars, which replace solid surfaces, can be used to locate extra discharge ports, which, if equipped with valves, allow the pump to change performance characteristics, simply by opening and closing of two valves. Thus, the chosen isobar determines the actual pumping chamber size, as well as pressure and flow, irrespective of the solid axial boundaries. It is interesting to note that the axially inner ports may be changed from discharge to suction, also simply opening and closing valves.
FIG. 1 shows some solutions to the previous problems. Just as in the centrifugal pump, the fluid may enter axially, where it gains rotational velocity driven by atmospheric pressure by the net positive suction head. As vanes rotate, they encounter the fluid in an intake plenum 10 tangentially, rather than at an angle to the fluid velocity, as the fluid tends to follow the rotating vacuum, created by the discharge of the rotating fluid chambers, and the fluid is moving by inertia outwardly, mostly by the NPSH, rather than by force from the leading edge of vane 7. The radial fluid speed is slowing but the rotational speed is increasing as the fluid becomes trapped inside chamber 15, which is then becomes zero velocity with respect to the rotor passages 15, and which then becomes chamber 15 which is bounded by vanes 7 and housing 1, or rather by an isobar 16 which is coincident with the cylindrical surface of housing 1, since the volute is eliminated. The cross-sectional area at 16 is larger than other cross-sectional areas in 15, so that the fluid does not increase in velocity at 16, as it does in centrifugal pumps, but is actually decreasing in radial velocity but, since the fluid is contained as positive displacement, it gains rotational velocity. Since the fluid is positively contained within chamber 15, it eliminates any relative motion between the trapped fluid within 15 and the vanes 7, such that the re-circulation problem has been dealt with. The removal of the volute, or at least the reduction in angular sector to equal only the discharge port 18, allows discharge only at 18, such that only the fluid with rotational velocity and inertial momentum is caused to exit tangentially through discharge port 18. Since the fluid velocity is the same as the rotor velocity, there is no chance for vortices to develop and to damage vane tips at 19. And while avoiding the problems described previously, the discharge velocity=vane tip velocity is at a maximum and is considerably greater than that of a centrifugal pump. This means the head pressure can be higher by the square of the difference, which is substantially higher. As previously noted, the pump rotational velocity was limited by the “suction specific speed” at 16, and with FIG. 1, there is no longer that speed restriction, and the main concern then becomes simply that the intake hose is large enough to accommodate the flow. The shape of vanes 7 and the shape of chamber 15 determines how close to a true positive displacement this pump becomes. The number of vanes 7 and chambers 15 can be significantly reduced, in fact can be reduced to one of each if desired. The mathematical analysis of the pump of FIG. 1 is simpler than that of centrifugal pumps and the results are consistent with theory. The tests show that this design is considerably more powerful than a single stage centrifugal, has much higher head pressure as well as having high flow rates.
I have included the following prior art: U.S. Pat. No. 2,982,224, which shows a kinetic positive displacement pump. U.S. Pat. No. 3,560,106 Sahlstrom 1971 which is a centrifugal pump for slurries.
U.S. Pat. No. 1,287,920 Duda which is a centrifugal pump having a tangential intake means. U.S. Pat. No. 1,215,881 Siemen 1917 which is a kinetic pump with self priming means.